Braun tube



Feb. 4, 1936.

K. SCHLESINGER BRAUN TUBE Filed Dec. 23, 1932 umwno 4 Patented Feb. 4,1936 UNITED STATES PATENT OFFICE Application December 23, 1932, SerialNo. 648,615 In Germany December 24, 1931 Claims.

The present invention relates to Braun tubes having a fluorescentpicture receiving screen.

Braun tubes are known wherein the fluorescent screen is made conductiveand is used as an anode 6 or is earthed for the purpose of avoiding anaccumulation of negative wall charges.

In these known Braun tubes there is arranged a thin metallic layerbetween the glass wall and the fluorescent layer. This metallic layercauses considerable losses of light produced by the cathode ray on thefluorescent substance.

Further, these known Braun tubes possess the disadvantage that thefluorescent substance may easily be burnt out in the case that thecathode 15 ray is directed for a longer time on to the same point of thefluorescent screen.

One object of the present inventionis to provide. a Braun tube whichallows of a more'iull utilization of the light produced in thefluorescent layer.

A further object of the invention is a Braun tube wherein a burning outof the fluorescent layer cannot occur.

Still further objects of the invention will be seen from the followingdescription.

According to the inventionfthere is employed as luminous screen anydesired luminous substance 01 a known kind, which substance is connectedwith the glass oi the bulb in the manner known per se by sintering in orby attaching said substance by means of water-glass preferably potassiumwater glass or the like, and is then furnished with an extremely thin,coherent metal coating. The thickness of this metal coating should besuch that the same offers the least possible resistance to the electrons(i. e., is as thin as possible), but on the other hand represents ahomogeneous, coherent reflectory surface. By means of this reflectorycoating it is accom- 40 plished that the whole of the light produced inthe fluorescent layer by the cathode ray is radiated towards thefront 1. e., towards the" spectator. The loss of intensity which iscaused upon the passage of the electrons through the 5 metal coating isrelatively small, and the e fiective radiating power of the tube is inthis manner ceteris paribus practically doubled by the reflectory effectof the metallic coating. The metal coating may consist of any desiredmetal having highly reflectory properties, such as copper, silver ortin, and may be deposited on the layer of fluorescent material by anydesired process of the known kind. Preferably there isemployed a thinsilver reflector, which is produced on the finished layer (i. e., thefluorescent layer already firmly connected with the glass wall of thetube by sintering, adhesives or the like) by means of a chemical processof the kind known per se (reduction of a suitable watery silver saltsolution) processes 01' this kind being described in nearly 5 eachmanual of chemistry, a full description or the particulars of said wellknown processes cannot be looked at as necessary. Naturally there mayalso be employed for the purpose of production any other known suitablemethod. 10 However, thin coatings of the requisite properties may beproduced in the most simple fashion with the use of the chemical processreferred to in the above.

The metallic coating of the invention may be employed as one anode ofthe tube.

In Figs. 1 and 2 there are shown two embodiments of the fluorescentscreen according to the invention, while Fig. 3 shows by way of exampleone form of embodiment of a Braun tube having a fluorescent screenaccording to the invention.

Fig. 1 shows an arrangement in which the luminous substance is sinteredinto the glass wall.

In the arrangement according to Fig. 2 the fluorescent layer isconnected with the glass, for example by cementing. In the drawing I isthe reflectory metal coating, 8 the fluorescent coating, and 9 theglass-wall of the Braun tube.

In Fig. 3, l is a thermionic cathode, 2 a Wehnelt cylinder, 3 and 4 twoanodes of equal potential, between which there are situated the pairs ofdeflecting plates 5 and 6, 'l the metallic reflector which is raised toa considerably higher potential and acts as third anode, 8 the luminouscoating, and 9 the wall of the tube.

Naturally, it is also possible to use only one or two anodesrespectively.

The luminous screen according to the invention, furnished with ametallic coating, is extremely insensitive to heat, provides aconsiderably greater intensity of light, and will endure for a muchgreater length of time than the known screens.

I claim:

1. A Braun tube for reproducing purposes comprising. an envelope, acathode and an anode mounted in operative relationship thereto, meansfor deflecting the cathode ray, a layer of a fluorescent substancemounted at one end of said envelope, and a thin, homogeneous, coherent,metallic coating mounted on the side of the fluorescent layer facingsaid cathode.

2. A Braun tube for reproducing purposes comprising an envelope, acathode and an anode mounted in operative relationship thereto, meansfor deflecting the cathode ray, a layer of a fluorescent substancemounted at one end of said envelope, and a thin, homogeneous coherent,metallic coating of highly reflectory properties mounted on the side ofthe fluorescent layer facing said cathode.

3. A Braun tube for reproducing purposes comprising an envelope, acathode and an anode mounted in operative relationship thereto, meansfor deflecting the cathode ray, a layer of a fluorescent substancemounted at one end of said envelope, and a thin, homogeneous, coherent,metallic coating permeable to electrons and of highly reflectoryproperties mounted on the side of fluorescent layer facing said cathode.

4. A Braun tube for reproducing purposes comprising an envelope, acathode and an anode mounted in operative relationship thereto, meansfor concentrating the cathode ray, means for controlling the cathoderay, means for deflecting the cathode ray, a layer 01' a fluorescentsubstance mounted at one end of said envelope, and a thin, homogeneous,coherent, metallic coating permeable to electrons and of highlyreflectory properties mounted on the side of the fluorescent layerfacing said cathode.

5. A Braun tube for reproducing purposes comprising an envelope, acathode and an anode mounted in operative relationship thereto, meansfor concentrating the cathode ray, means for controlling the cathoderay, means for deflecting the cathode ray, 9, layer or a fluorescentsubstance mounted on the bottom oi. said envelope, and a thin,homogeneous, coherent, metallic coating permeable to electrons and ofhighly reflector-y properties mounted on the side 01' the fluorescentlayer facing said cathode said metallic coating being adapted to beconnected with a high positive potential.

, KURT SCI-ILESINGER.

